You can't motivate someone by underpaying him. That's a disincentive, not an incentive. And it doesn't matter if you're making $40k/yr. or $140k/yr., you're still going to worry about losing your job.

As far as paying the elderly and crippled starvation wages ... I'm sorry, but I'm going to have to drop my management training for a moment and ask if you're serious. If you are, then you should know that there are laws that specifically protect these people. Even if you don't care, you don't want your business to make the papers because it's getting sued for that sort of thing.

Most of the people who take these starvation-wage jobs are temporary workers. They're students who are working part time to supplement other means of support. They'll be gone when summer break comes. They're migrant workers who are living in crowded, unsafe, gray-market housing. They'll be taking their money back home as soon as the busy season is over. They're people who have been laid-off and are trying to burn through their savings more slowly. They'll be gone as soon as they can find a job in their old industry.

If you want those employees you've hired and trained to stick around, you have to pay at least a living wage. If you're smart, you'll pay more and find other ways to make your business more attractive to workers than the other businesses in your industry. Every employee that leaves is leaving for a competitor. Let the dumb managers driver away their trained employees. You want to make sure the good ones are working for you.